There is no ruler in the current version. It is highly demanded and we will add it in the following updates.

Here is how I like to check distances:

- Place the origin on the reference location. To do so, click on the origin in the tool bar and choose one of the five snap options available in the snap tool bar. You can also use the number block of your keyboard to snap onto an edge of your front panel. 7 stands for top/left, 6 for center/right, 5 for center etc.

- Once you have the origin in the reference location click on the object you would like to know the distance to. You can read the distance (coordinates) in the object properties side window (activate in 'View')

I hope that helps until we will have a ruler available in Front Panel Designer.